Hyaluronic acid for biorevitalization

Vladimirs Khabarovs, Doctor of Chemical Sciences, Director of the UN "Hyaluronic Acid Scientific Research Center", Moscow

Classically, biorevitalization is considered "...a method of intracutaneous injection of unmodified hyaluronic acid (hyaluronal), which helps to restore the physiological environment and normal metabolic processes in the dermis".

More than 10 years of experience in using native hyaluronic acid for biorevitalization allows us to determine the main properties of these preparations. This is especially important in today's conditions, when dozens of biorevitalizers are offered on the market of injectable preparations for aesthetic medicine, which differ from each other in terms of concentration, molecular weight, source of hyaluronic acid.

REASONS FOR USING HYALURONIC ACID FOR BIOREVITALIZATION

Aesthetic medicine offers anti-age or anti-aging programs that work not only on existing skin damage, but also on the stimulation and optimization of the skin's natural abilities. Undoubtedly, one of the main methods that solves these problems is biorevitalization. The main purpose of using this method is replenishing tissue fluid reserves and creating optimal conditions for improving cell functioning, which means also activation of endogenous hyaluronic acid synthesis and synthesis of other intercellular matrix components in the dermis.

The intercellular matrix is ​​a dynamic system. Its structures are constantly renewing themselves at different speeds - collapsing and at the same time forming anew/synthesizing. The consistency or immutability of the structures of the dermis cells, like the homeostasis of the whole organism, is based on continuous catabolism and anabolism processes. Thanks to the perfection of the organism's mutual interaction, regulation, and coordination system, which ensures these catabolism and anabolism processes, maintenance of internal matrix parameters within normal limits is ensured. An irreplaceable condition for maintaining the stationary state of the cell, or cell homeostasis, is the exchange of substances and energy. And, most importantly, substrate deficiency or excess of metabolites, such as hyaluronic acid, are stress factors that can cause disturbances in the regulation of metabolism and regeneration of cell structures in the dermis. Including the excess amount of exogenous hyaluronic acid can lead to an unwanted effect.

HOW TO DETERMINE THE OPTIMAL QUANTITY OF HYALURONIC ACID / THE OPTIMAL QUANTITY OF HYALURONIC ACID IMPLEMENTATION

Taking into account the above, it becomes clear that the amount of hyaluronic acid administration is a very important parameter when performing anti-aging procedures. In connection with this, at the Scientific Research Institute of General Pathology and Pathophysiology of the Russian Academy of Medical Sciences, under the leadership of Doctor of Medical Sciences AA Moskovtsev, work was developed in which the effect of hyaluronan concentration on the viability of fibroblasts was studied.

Figure 1. Metabolic activity of EA.hy926 endotheliocytes (curve 1, 2) and metabolic activity of epidermal/epidermal fibroblasts (curve 3, 4) after 24h and 48h exposure to different concentrations of hyaluronic acid preparations, respectively.

The results presented in the figure demonstrate that an increased concentration of hyaluronan in tissue culture (above 0.5 wt% or 5 mg/ml) leads to a dose-dependent decrease in fibroblast survival. 2 mass % hyaluronic acid concentration results in 20-25% cell death. The main function of dermal fibroblasts is participation in the metabolic processes of intercellular substances. The state and function of the main connective tissue extracellular matrix components - collagen, elastin, reticular fibers and intercellular matrix - depend on the functional activity of fibroblasts.

HOW TO CORRECTLY CALCULATE THE OPTIMAL QUANTITY OF HYALURONIC ACID FOR PERFORMING THE PROCEDURE?

It is obvious that a decrease in the metabolic activity of cell structures can lead to an imbalance of catabolism and anabolism processes. It is necessary to avoid unwanted overdose of the preparation, so it is necessary to know exactly what amount of biorevitalizer will be safe for the patient to use when administering the preparation by injection. Let's evaluate what amount of hyaluronan can be administered to a patient at one time. If the approximate dimensions of the injection zone are 20x20 cm (400 cm2), then at the average thickness of the dermis - 4 mm - the volume of the dermal layer reaches 160 cm3. The physiological concentration of hyaluronic acid in the dermis is 0.05% by mass (0.5 mg/ml). Thus, the physiological concentration of hyaluronal in the injection area is 160 cm2 x 0.5 mg/cm3 = 80 mg.

Countless studies prove that the age-related amount of endogenous hyaluronic acid in the patient's skin becomes noticeable only after the age of 60, but the main/other fluctuations in the amount of hyaluronic acid occur in connection with seasonal factors (including/especially, the decrease in the content of hyaluronic acid in the skin during the summer period occurs mainly due to ultraviolet radiation as a result). These quantity fluctuations make up 15-20% of the corresponding physiological quantity. It follows that the maximum biorevitalizing effect can be achieved/is achievable by administering 2-2.5 ml of 0.5% or 1-1.5 ml of 1% hyaluronan hydrogel.

It is important to note/take into account that 1% (10 mg/ml) hyaluronic acid solution is the maximum concentration of the biorevitalizer. Let's explore this fact in more detail.

The properties of hyaluronan macromolecules are well known, even at relatively low concentrations (0.05-0.1 mass %) - to form viscous hydrogel structures in aqueous solutions. A hyaluronic acid molecule with a molecular weight of 1-1.5 parts per million Da is able to absorb at least 100 times more water compared to its own weight. Thus, in a 1% hyaluronan solution, all water is in bound form. Its macromolecules in such a solution have a considerable diversity of conformation, but as a rule, they form a semi-solid ball structure. When forming more or less solid balls, the polysaccharide molecules attract a huge amount of water, forming relatively large domains.

WHY IS IT BAD TO GIVE TOO MUCH HYALURONIC ACID?

As shown by hydrodynamic studies, the real density of hyaluronan chains in the molecular domain is not high (approximately 0.1-0.5% by mass), but depends on the molecular mass itself. When such a gel is introduced into the skin, the divalent calcium and magnesium ions of the intercellular matrix of the dermis bind to the added hyaluronic acid molecules and form the transverse ionic seams of the polymer chains. As the transverse ion seams increase, the gel acquires a difficult-to-dissolve bulky structure. At the same time, the size of its pores decreases, which makes it difficult for the permeability of such a structure to cleavage enzymes (hyaluronidase). As a result, the placement of the gel in the intercellular space of the dermis and the catabolism of hyaluronic acid also slow down.

When the concentration of hyaluronic acid in the gel increases, especially by 1% by mass, a dense intermolecular lattice is formed, which results in a significant increase in its viscosity. In concentrated hydrogels, hyaluronic acid can no longer exist as an independent substance and form different spatial structures. Only those conformations are possible in which each disaccharide bond of each molecule spatially occupies only the space not occupied by adjacent neighboring molecules. Therefore, in concentrated solutions, the molecular balls are significantly intertwined with each other and in some places form areas where the amount of water is reduced. In these areas, hyaluronic acid is as if not completely dissolved and forms a compressed sponge-like structure. When such hydrogels enter the water environment (the dermis consists of 70-80% water), the hyaluronic acid balls straighten, creating an energetically more favorable conformation, and begin to attract water from the intercellular (interstitial) space of the dermis. (The same thing happens when a compressed sponge is released from a deforming source.) Thus, intracutaneously injected highly concentrated hyaluronic gels promote, paradoxically, not an increase in dermal hydration, but on the contrary - a decrease in hydration in the dermis. This has been proven in the results of clinical studies conducted in 2008 at the Institute of Plastic Surgery and Cosmetology of the Ministry of Health of the Russian Federation under the leadership of VG Zmazova.

A biorevitalizer with a concentration of 1.4% hyaluronic acid and a molecular weight of 1.6 parts per million Da was used for testing. Apparatus measurements of skin quality characteristics were performed dynamically - before application of the investigational preparation and 2.4 weeks after administration of the investigational preparation. In all patients, the level of skin hydration decreased during the first 2 weeks after the injection (by 8-14%). 2 weeks after the injection, the patients' skin hydration level gradually started to increase, at the end of the 4th week it increased by 12-15% compared to the initial parameters. These data show that as soon as the amount of exogenous (administered) hyaluronic acid decreased to a normal physiological level as a result of biodegradation, the preparation began to have a revitalizing effect. Such a dose-dependent effect can lead to various negative consequences.

HOW CAN EXCESS HYALURONIC ACID HARM?

Avicenna's well-known saying "Everything is poison and everything is medicine" accurately describes the fact that the physiological effects of various chemical compounds and physical factors are, as a rule, dose-dependent. As a result of the introduction of a significant amount of hyaluronic acid, there is a redistribution of interstitial water in the intercellular matrix, which is an important stress factor of the dermis. Instead of "...achieving the skin revitalization effect and, due to the creation of a high-quality intercellular matrix and the increase in the proliferative activity of fibroblasts within the genetically programmed framework, increasing the skin's adaptability", as reflected in various articles on biorevitalization, injections of large amounts of hyaluronic acid preparations do the exact opposite leads to destabilization of tissue and cell homeostasis.

When fibroblasts and other structural elements of the dermis lose water, the pH, ion composition, and strength of intercellular matrix ions change, which can interfere with the normal functioning and activity of matrix proteins due to changes in protein structure or partial denaturation. Hydrophobic amino acids - tryptophan, tyrosine, phenylalanine - are located on the surface of protein aggregates, which are usually located inside the macromolecule in the three-dimensional structure of the protein. The mentioned amino acids actively absorb ultraviolet radiation with a wavelength of 280 nm, so proteins become more sensitive to the relevant spectrum. As a result, unstable protein conformational changes occur, leading to protein aggregation and the formation of abnormal protein deposits (amyloid). As a result of energy transfer processes promoted by ultraviolet radiation, hydrophobic amino acids can participate in the formation of singlet oxygen - this is the active form of oxygen that participates in oxidative stress processes. Singlet oxygen, the precursor of the hydroxyl radical, promotes the formation of intermolecular crosslinks in the intercellular proteins of the dermis. This is a very unfavorable process that leads to the deterioration of the physico-chemical properties of collagen, the reduction of its elasticity and ability to swell, and the formation of resistance to collagenase, thus contributing to the development of collagenosis.

The data presented in the article convincingly indicate how important a parameter hyaluronan concentration is in biorevitalization preparations when performing aesthetic procedures. In practice, it is possible to determine whether an overdose of the biorevitalizer has occurred by how long the papules remain after the injection. If the papule formed at the injection site is not absorbed within a couple of days, then this is a direct indication of an excess amount of injected hyaluronic acid.

Human skin is the organ that first suffers from negative environmental factors. It has a high potential for adaptation and regeneration. Therefore, after one administration of an increased dose of hyaluronan, of course, significant negative effects will not be observed. However, we must not forget that biorevitalization courses usually include 3-5 injection procedures and occur periodically 2-3 times a year. Such "anti-aging" biorevitalizing injections with an increased permissible dose of hyaluronic acid, applied over several years, can significantly worsen the patient's skin condition. Our task is to draw the attention of cosmetologists and patients themselves to the possible consequences of such procedures.

It should be remembered that papules that are not absorbed for a long time after the introduction of the biorevitalizer are not only a cosmetic defect, but a serious reason to refuse the use of such a preparation. When looking at this topic, a question may naturally arise - can a similar situation develop using hyaluronic acid-based fillers, considering that the concentration of polysaccharide in them is 2% or more? When using fillers, there is little chance that this type of problem would occur, because the sorbing power of unmodified hyaluronic acid is many times lower.

The article is based on http://www.beauty-face.ru/ materials